v1.2.0 / 01 jan 03 / greg goebel / public domain
* While fighter aircraft tend to become larger and more expensive as their users demand more of them, there have always been a few aircraft designers who believe that a simple, lightweight fighter might find a useful niche.
One of the more interesting of these lightweight fighters was the British Folland (later Hawker-Siddeley) "Gnat". Although it was never used as a fighter by the British Royal Air Force (RAF), it did achieve success with the RAF in its "Gnat T.1" trainer version, as well as wide recognition as the mount for the RAF Red Arrows aerobatic team.
The Gnat also achieved export success, particularly with India, which manufactured the aircraft under license. In fact, the Indians found the Gnat so capable that they designed and built their own improved version, the "Ajeet". This document outlines the history of the Gnat and AJeet.
* The Gnat was the creation of W.E.W. "Teddy" Petter, a British aircraft designer who had gained wide recognition for his design of the English Electric Canberra bomber and other aircraft. Petter had grown suspicious of the trend towards bigger and more expensive combat aircraft, and he felt that a small, simple fighter would offer the advantages of low purchase and operational costs. New lightweight turbojet engines were being developed that would be able to power such small fighters.
Petter was unable to pursue this vision at English Electric, so he left to become managing director of Folland Aircraft. In 1951, using company funds, he began work on his lightweight fighter concept, which he designated the "Fo-141 Gnat". The Gnat was to be powered by a Bristol BE-22 Saturn turbojet with 16.9 kN (1,724 kg / 3,800 lb) thrust.
However, the Saturn was cancelled, and so Petter's unarmed proof-of-concept prototype for the Gnat was powered by the less powerful Armstrong Siddeley Viper 101 with 7.3 kN (744 kg / 1,640 lb) thrust. The prototype was designated the "Fo-139 Midge". The Midge first flew on 11 August 1954 with Teddy Tennant at the controls, and proved to be an excellent aircraft.
The Midge had a number of advanced features, such as hydraulically powered
"flaperons", main gear that could be used as airbrakes, and a one-piece
canopy that hinged over an inner armored windscreen. Despite the
underpowered engine, the little jet could break Mach 1 in a dive and was
superbly maneuverable.
FOLLAND FO-139 MIDGE:
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spec metric english
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wingspan 6.30 meters 20 feet 8 inches
length 8.76 meters 28 feet 9 inches
height 2.82 meters 8 feet 1 inch
max takeoff weight 2,041 kilograms 4,500 pounds
maximum speed 986 KPH 600 MPH / 522 KT
service ceiling 11,580 meters 38,000 feet
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However, the Midge had demonstrated that Petter's lightweight fighter concept had much going for it. Folland went on to develop a full-scale Gnat prototype, also using company funds.
* The full-scale aircraft, designated the "Fo-145 Gnat", performed its
initial flight on 18 July 1955, again with Tennant at the controls. It was
very similar to the Midge, but had a maximum takeoff weight about twice as
large. It was powered by a preproduction Bristol Orpheus turbojet with 14.6
kN (1,490 kg / 3,285 lb) thrust.
FOLLAND FO-145 GNAT:
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spec metric english
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wingspan 6.73 meters 22 feet 1 inch
length 9.04 meters 29 feet 8 inches
height 2.46 meters 8 feet 1 inch
empty weight 2,180 kilograms 4,800 pounds
max loaded weight 4,100 kilograms 9,040 pounds
maximum speed 1,120 KPH 695 MPH / 605 KT
service ceiling 13,720 meters 45,000 feet
combat radius with drop tanks 800 KM 500 MI / 435 NMI
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The Gnat prototype was refitted with an uprated preproduction Orpheus engine to put on flight displays at the Farnborough air show that year. While the RAF had no requirement for such a machine, the government wanted to encourage Folland in their work, and so the British Ministry of Supply (MOS) ordered six prototypes of the full-development aircraft for evaluation. The number was later increased to eight.
The evaluation Gnats were powered by the production-spec Bristol Orpheus 701 turbojet with 20.1 kN (2,042 kg / 4,502 lb) thrust. Most of the test flights were conducted in the UK, though ground-attack trials were performed in Aden.
The report from the RAF evaluation generally praised the Gnat's performance, but there was no consensus that the Gnat was what the RAF needed. The Gnat fighter never served operationally in Britain, though the MOS did order two more Gnats on top of the original order for six.
* Nonetheless, the good press given the Gnat opened the way for export sales. Two were sold to Yugoslavia for evaluation, and thirteen were sold to Finland. The Finnish Gnats were delivered in 1958 and 1959, and two of them were configured for reconnaissance, with noses carrying three 70 millimeter cameras. Finland operated its Gnats until 1972.
India was very interested in the Gnat, and in 1956 Folland and Hidustan Aircraft Limited (HAL) signed a license agreement, beginning a long love affair between India and the Gnat. 25 Folland-built Gnats, including two hand-me-downs from the RAF evaluation program, and 20 kits were sold to India through HAL, with these machines powered by the further uprated Bristol Orpheus 701-01 engine with 20.93 kN (2,134 kg / 4,705 lb) thrust.
The Gnat went into IAF service in the spring of 1958, with the first Gnat assembled by HAL from a kit flying in Bangalore on 18 November 1959. HAL then went on to build 195 Gnats themselves up to early 1974. The first completely HAL-built Gnat flew on 21 May 1962. IAF pilots were delighted with the nimble Gnat, which they felt was more than a match for Pakistani F-86s and MiG-19s, and nicknamed it the "Saber Slayer".
* The RAF had shown no real interest in the Gnat fighter, but Teddy Petter was persistent, and proposed the tandem-seat "Fo-144" trainer version of the Gnat. The RAF liked the idea, and a contract for 14 preproduction "Gnat T.1" trainers was placed in 1958. The first performed its initial flight on 31 August 1959.
The Gnat T.1 had no gun armament, but retained the twin stores pylons. It
was powered by a Bristol Orpheus 4-100 engine with 18.8 kN (1,920 kg / 4,230
lb) thrust; a larger tail; and a bigger wing with integral fuel tanks, 40%
greater wing area, and conventional ailerons and flaps rather than flaperons.
FOLLAND FO-145 GNAT T.1 TRAINER:
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spec metric english
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wingspan 7.32 meters 24 feet
length 9.68 meters 31 feet 9 inches
height 2.93 meters 9 feet 8 inch
empty weight 2,331 kilograms 5,140 pounds
max takeoff weight 3,915 kilograms 8,630 pounds
max speed at altitude 1,024 KPH 636 MPH / 553 KT
service ceiling 14,630 meters 48,000 feet
range with drop tanks 1,852 KM 1,151 MI / 1,000 NMI
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Five yellow-painted Gnat T.1s modified to generate smoke were used in 1964 by the RAF "Yellojacks" aerobatic demonstration team, which was redefined a year later to the RAF "Red Arrows", with red-painted aircraft. Their nine red Gnats, trailing smoke during precision maneuvers, pleased crowds at airshows in Britain and around the world. The Red Arrows operated the Gnat until 1979, when they converted to the British Aerospace Hawk, which also replaced the Gnat T.1 in the advanced training role.
The Gnat T.1 served the RAF well, though it suffered from high maintenance costs. It had not been designed to be easy to maintain, and some of its systems were not noted for their reliability. Its cockpit was also cramped and instructor's forward visibility was poor. The BAe Hawk was designed specifically to provide the utility of the Gnat T.1, while lowering operational costs and eliminating some of the Gnat's defects.
* The IAF was very happy with the Gnat, but the little fighter did have its problems, the worst being that its hydraulics and some of its control systems were unreliable. In 1972, the IAF issued a requirement for an improved "Gnat II", at first specifying that the new version was to be optimized as an interceptor, but then expanding the specification to include the ground-attack role.
HAL modified two Gnats for testing subsystems for the new design, and the first example of the new type flew on 6 March 1975. The improved Gnat was named "Ajeet", Sanskrit for "Invincible / Unconquered / Unbeatable", and the two initial prototype Ajeets were modified from the last production Gnats built by HAL. The first production Ajeet flew on 30 September 1976, and deliveries to the IAF began in 1977. A total of 79 Ajeets were built by the time production ended in 1982, and ten Gnats were upgraded to Ajeet standards.
The Ajeet was difficult to tell apart from a Gnat at a casual glance, but it incorporated many changes and improvements. The most visible change was that the Ajeet had four stores pylons, with a total carriage capacity of 900 kilograms (one ton), instead of the Gnat's two stores pylons.
Other significant changes included improved hydraulics and controls, use of the Martin-Baker Mark GF4 ejection seat instead of the Folland-designed Type 2G; new avionics, including a modern Ferranti gunsight; a slab tail; improved landing gear with an antiskid braking system; and fuel tanks built into the wings, with each integral wing tank storing 250 liters (66 US gallons) of fuel.
The integral wing tanks meant that all four stores pylons could be used for weapons. The small size of the Gnat had meant limited range without drop tanks, and with the Gnat's two stores pylons drop tanks meant no weapons other than cannon. The Ajeet was much better suited to the ground attack role than the Gnat.
* HAL also designed a two-seat trainer version of the Ajeet, with a lengthened fuselage and a tandem dual-cockpit design. Two internal fuel tanks were deleted to accommodate the second cockpit. The two 30 millimeter cannon and the four stores pylons were retained, though the cannon could be removed and replaced with additional fuel tanks. The trainer used the same Orpheus 701 engine as the Gnat and Ajeet fighters.
The Ajeet trainer never reached production. One prototype was built in 1982 and crashed in that year, a second prototype flew in 1983, and then the program went into limbo and eventually died. Some sources claim that 30 Ajeet trainers were built, but this is hard to believe. The IAF's s requirement for an advanced trainer remained unfilled through the 1980s and 1990s, until the service settled on the BAE Hawk.
The last Ajeets were phased out of IAF service in 1991. No Gnats or Ajeets remain in operational service. However, a number of Gnats, mostly ex-RAF T.1s, have ended up in private hands as a thrilling high-class toy, and make occasional appearances at airshows.
* Sources include:
Various small pieces of information were found in other sources such as JANE'S ALL THE WORLD AIRCRAFT, but no one of them added more than one or two pieces to the puzzle, and so I have not cited them.
* Revision history:
v1.0 / 01 nov 99 / gvg
v1.1 / 01 sep 00 / gvg / Cleanup, minor changes.
v1.2.0 / 01 jan 03 / gvg / Cosmetic update.